Vent members are attached to housings that accommodate therein electrical components of an automobile, such as lamps, sensors, and ECUs, in order not only to ensure ventilation between the interior and the exterior of the housings but also to prevent the entry of foreign matter into the interior of the housings. Examples of such vent members are disclosed in JP 2004-47425A, JP 10-85536A, and JP 2001-143524A.
For instance, as is shown in FIG. 14, the vent member disclosed in JP 2004-47425A includes a support body 103 on which a permeable membrane 102 is disposed and a cover part 104 attached to the support body 103 so as to cover the permeable membrane 102. The vent member 101 configured as above is fixed to an opening 107 of a housing 106 via an O-ring 105. By allowing a gas to permeate through the permeable membrane 102, it is possible to ensure ventilation between the interior and the exterior of the housing 106. The cover part 104 prevents damage to the permeable membrane 102 caused by an external force and deterioration to the permeability of the permeable member 102 caused by deposition of dust.
In recent years, there has been a need for vent members that are more excellent in durability against foreign matter. For example, as vent members to be used for the housings of lamps and ECUs in an automobile, there is a need for vent members not only capable of withstanding car washing, in particular, high-pressure car washing, but also capable of completely preventing the entry of water into the interior of the housings.
Regarding the vent member 101 shown in FIG. 14, because the cover part 104 covers the permeable membrane 102 directly above, it stands strong against foreign matter, such as water droplets falling down from directly above. However, because it opens widely in the lateral direction, it is highly likely that foreign matter coming from the side applies a direct impact to the permeable membrane 102. In addition, once the foreign matter adheres onto the permeable membrane 102, it remains on the permeable membrane 102 and can cause deterioration of the permeability.
Meanwhile, the vent members disclosed in JP 10-85536A and JP 2001-143524A are configured in such a manner that the permeable membrane is covered completely with a tubular cover part. It is therefore less likely that foreign matter, such as water droplets, applies a direct impact to the permeable membrane. However, the configuration that resists the entry of foreign matter into the interior of the cover part can bring out an adverse effect in some cases. More specifically, once the foreign matter enters the interior of the cover part, the foreign matter will not be readily discharged to the exterior of the cover part or it frequently remains on the permeable membrane and on the inner surface of the cover part.
In addition, the vent members disclosed in JP 10-85536A and JP 2001-143524A fail to achieve sufficient dust-proof and water-proof effects unless they are used in a posture in which the cover part is oriented vertically upward. When used in a posture in which the cover part is oriented vertically downward, foreign matter can enter the interior of the cover part with relative ease. In short, the vent members disclosed in JP 10-85536A and JP 2001-143524A have limitations of use that are absent with the vent member shown in FIG. 14.